sendmail, 4th Edition

$g

The sender’s address relative to recipient All versions

The $g macro is identical to $f except that it undergoes additional rule-set processing to translate it into a full return address. During delivery the sender’s address is processed by the canonify rule set 3, the rule set 1, and the final rule set 4, and then placed into $f. That rewritten address is further processed by the canonify rule set 3 and rule set 1 again, then rewritten by the rule set specified in the S= equate of the delivery agent. Finally, it is rewritten by the final rule set 4, and the result is placed into $g.

$g holds the official return address for the sender. As such, it should be used in the From: and Return-Path: header definitions.

The S= equate for each delivery agent must perform all necessary translations to produce a value for $g that is correct. Because the form of a correct return address varies depending on the delivery agent, other rule sets should generally not be used for this translation.

Ordinarily, RFC2822 comments (Comments in the Header Field on page 1125) are restored when $g is used in headers. To omit those comments (perhaps for security reasons) you can use the F=c delivery agent flag (F=c on page 768).

$g is transient. If it is defined in the configuration file or in the command line, that definition can be ignored by sendmail. Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&g, not $g).